Mechanical polishing method and mechanical polishing device for SOI wafer

Abstract

The present invention provides a mechanical polishing method and a mechanical polishing apparatus for an SOI wafer, the mechanical polishing process comprising a coarse polishing process in which the relationship between the cutting speed of a coarse polishing wheel and the rotational speed of a polishing stage satisfies a preset condition, and the relationship between the cutting speed of the coarse polishing wheel and the rotational speed of the polishing stage satisfies a preset condition. The thickness of the face, away from the supporting wafer, of the device wafer is reduced to the preset thickness in the mechanical grinding process, and the damage area of the face, away from the device wafer, of the supporting wafer is smaller than a preset threshold value. According to the invention, the problem that the performance and the reliability of the device are influenced due to large damage to the back surface of the SOI wafer in a mechanical grinding process can be solved, that is, the damage to one surface, far away from the device wafer, of the support wafer in the SOI wafer is obviously improved, and the performance and the reliability of the device are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a mechanical grinding method and a mechanical grinding device for an SOI wafer. Background Art

[0002] Silicon on insulator (SOI) technology has become one of the mainstream products in most electronic materials fields. SOI is an integrated circuit manufacturing technology that achieves insulation between the silicon layer and the substrate by growing a thin silicon layer on an insulating substrate. SOI technology can improve the performance and reliability of integrated circuits, reduce power consumption and noise, and achieve a smaller device size. With the rapid development of new energy vehicles, the integration of automotive-grade SOI material on-board chips has gradually increased. Therefore, the market demand for high-uniformity SOI is getting higher and higher. How to further improve the uniformity of SOI materials has become an important trend in current development.

[0003] At present, SOI wafers of target thickness are generally obtained through mechanical grinding and polishing processes. Mechanical grinding and polishing processes need to consider the thinness of the silicon layer and the surface flatness. Uneven thickness of the top silicon layer may cause unstable device performance, inconsistent current density of local electron channels, uneven thermal effects and even line width changes. Since the top silicon layer of the SOI wafer is very thin, usually only a few microns thick, the mechanical grinding process causes greater damage to the back of the SOI wafer, thus affecting the performance and reliability of the device. Summary of the invention

[0004] The purpose of the present invention is to provide a mechanical grinding method and a mechanical grinding device for SOI wafers, so as to solve the problem that the back side of the SOI wafer (with or without an insulating layer) is severely damaged during the mechanical grinding process, thereby affecting the performance and reliability of the device.

[0005] In order to solve the above technical problems, the present invention provides a method for mechanically grinding an SOI wafer, comprising: Providing an SOI wafer, the SOI wafer comprising a support wafer and a device wafer, and a buried oxide layer located between the support wafer and the device wafer; Performing a mechanical grinding process to reduce the thickness of the side of the device wafer away from the support wafer to a preset thickness and a damage area of ​​the side of the support wafer away from the device wafer is smaller than a preset threshold; Wherein, the mechanical grinding process includes a rough grinding process, in which the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding carrier meets a preset condition.

[0006] Optionally, the preset conditions satisfied by the relationship between the cutting speed of the rough grinding wheel and the rotational speed of the grinding platform include: when the rotational speed of the grinding platform is greater than the preset rotational speed, reducing the cutting speed of the rough grinding wheel; when the rotational speed of the grinding platform is less than the preset rotational speed, increasing the cutting speed of the rough grinding wheel.

[0007] Optionally, the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform satisfies the preset condition: Y=BA*X; Wherein, X is the lowering speed of the rough grinding wheel, Y is the rotation speed of the grinding platform, A is the change in the rotation speed of the grinding platform corresponding to the change in the lowering speed of the rough grinding wheel per unit, B is the safety window of the rotation speed of the grinding platform, 5≤A≤10, 100≤B≤200, 3μm / s≤X≤10μm / s.

[0008] Optionally, the mesh size of the rough grinding wheel is 50 to 800 meshes, and the spindle speed is 500 rpm to 4000 rpm.

[0009] Optionally, the mechanical grinding process further includes a fine grinding process, in which the mesh size of the fine grinding wheel is 1500 to 10000, and the spindle speed is 500 rpm to 4000 rpm.

[0010] Optionally, after performing the mechanical grinding process, the thickness of the device wafer in the SOI wafer is greater than 12 μm, and the total thickness variation of the SOI wafer is less than 1.5 μm.

[0011] Optionally, the thickness of the supporting wafer in the SOI wafer is 772 μm to 777 μm, and the total thickness variation of the supporting wafer in the SOI wafer is less than 0.4 μm.

[0012] Based on the same inventive concept, the present invention also provides a mechanical grinding device for executing any of the above-mentioned mechanical grinding methods for SOI wafers, comprising a rough grinding wheel and a grinding carrier, wherein the relationship between the lowering speed of the rough grinding wheel and the rotational speed of the grinding carrier satisfies a preset condition, so as to thin the thickness of a side of the device wafer away from the supporting wafer to a preset thickness and the damage area of ​​the side of the supporting wafer away from the device wafer is less than a preset threshold.

[0013] Optionally, the preset conditions satisfied by the relationship between the cutting speed of the rough grinding wheel and the rotational speed of the grinding platform include: when the rotational speed of the grinding platform is greater than the preset rotational speed, reducing the cutting speed of the rough grinding wheel; when the rotational speed of the grinding platform is less than the preset rotational speed, increasing the cutting speed of the rough grinding wheel.

[0014] Optionally, the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform satisfies the preset condition: Y=BA*X; Wherein, X is the cutting speed of the rough grinding wheel, Y is the rotation speed of the grinding platform, A is the change in the rotation speed of the grinding platform corresponding to the change in the cutting speed of the rough grinding wheel per unit, and B is the safety window of the rotation speed of the grinding platform, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

[0015] In the mechanical grinding method of SOI wafer provided by the present invention, the mechanical grinding process includes a rough grinding process, in which the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform meets the preset conditions, so that the thickness of the side of the device wafer away from the supporting wafer is thinned to a preset thickness in the mechanical grinding process and the damage area of ​​the side of the supporting wafer away from the device wafer is less than a preset threshold. The present invention can solve the problem that the damage to the back of the SOI wafer is large in the mechanical grinding process, affecting the performance and reliability of the device, that is, the damage to the side of the supporting wafer away from the device wafer in the SOI wafer of the present invention is significantly improved, thereby improving the performance and reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Those skilled in the art will appreciate that the drawings are provided for a better understanding of the present invention, but do not constitute any limitation on the scope of the present invention.

[0017] Figure 1 This is a diagram showing the effect of the knife lowering speed and the rotation speed of the grinding platform on the damage to the back side of the SOI wafer in an embodiment of the present invention.

[0018] Figure 2 This is a back side damage diagram of the SOI wafer in the first group of embodiments of the present invention.

[0019] Figure 3 This is a back side damage diagram of the SOI wafer in the second group of embodiments of the present invention.

[0020] Figure 4 This is a back side damage diagram of the SOI wafer in the third group of embodiments of the present invention.

[0021] Figure 5 This is a damage diagram of the back side of the SOI wafer in the fourth group of embodiments of the present invention.

[0022] Figure 6 It is a flow chart of a mechanical grinding method for an SOI wafer according to an embodiment of the present invention.

[0023] Figures 7 and 8 It is a schematic structural diagram corresponding to the steps of the mechanical grinding method for SOI wafer according to an embodiment of the present invention.

[0024] Fig. 9 Schematic diagram of the structure of a mechanical grinding device according to an embodiment of the present invention.

[0025] In the attached drawings: 10 - support wafer; 11 - first buried oxide layer; 20 - device wafer; 21 - second buried oxide layer; 30 - mechanical grinding device; 31 - grinding platform; 32 - coarse grinding wheel. DETAILED DESCRIPTION

[0026] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0027] As used in the present invention, the singular forms "one", "an" and "the" include plural objects, the term "or" is usually used to include the meaning of "and / or", the term "several" is usually used to include the meaning of "at least one", and the term "at least two" is usually used to include the meaning of "two or more". In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined as "first", "second" and "third" can explicitly or implicitly include one or at least two of the features. In addition, as used in the present invention, an element is arranged on another element, which usually only indicates that there is a connection, coupling, matching or transmission relationship between the two elements, and the connection, coupling, matching or transmission between the two elements can be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, an element can be in any orientation such as inside, outside, above, below or on one side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] The inventors have found that in the mechanical grinding process, the thickness of the top silicon layer of the SOI wafer is very thin, usually only a few microns. Mechanical grinding is needed to thin the device wafer with a thickness of about 775μm to the target value. The amount of material removed by mechanical grinding is huge, and the grinding time is too long. The back support wafer of the SOI wafer is always in contact with the grinding carrier, which can easily cause irreversible damage to the polished surface on the back. These damages are prone to risks of falling off and breaking in subsequent processes, causing contamination or even scrapping of the SOI wafer, and even causing huge losses in the subsequent device process.

[0029] In the mechanical grinding process, the mechanical grinding process includes a rough grinding process and a fine grinding process. Since the contact pressure between the SOI wafer and the grinding platform is relatively large in the rough grinding process step, the degree of damage to the back side of the SOI wafer (the side of the supporting wafer away from the device wafer) is mainly affected by the rough grinding process step. In the traditional rough grinding process, the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform will cause damage to the back side of the SOI wafer. Usually, it is optimized by adjusting the lowering speed of the rough grinding wheel or the rotation speed of the grinding platform separately. However, when the lowering speed is increased in order to shorten the processing time, obvious damage will inevitably appear on the insulating layer on the back side of the SOI wafer. Therefore, the inventor speculates whether there is a process window with a matching relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform, so that there is no obvious damage to the back side of the SOI wafer after grinding, thereby expanding the process window.

[0030] The inventors conducted experimental research on two influencing factors, namely, the knife lowering speed of the rough grinding wheel and the rotational speed of the grinding carrier, designed a DOE experiment, and obtained a large amount of experimental data. The experimental data show that whether the back side of the SOI wafer is damaged after grinding is significantly correlated with the knife lowering speed of the rough grinding wheel and the rotational speed of the grinding carrier. When the knife lowering speed of the rough grinding wheel in the rough grinding process step is controlled within the range of 3μm / s to 10μm / s, the rotational speed Y of the grinding carrier and the knife lowering speed X of the rough grinding wheel satisfy the formula Y=BA*X, wherein X is the knife lowering speed of the rough grinding wheel, Y is the rotational speed of the grinding carrier, A is the change in the rotational speed of the grinding carrier corresponding to the change in the knife lowering speed of the unit rough grinding wheel, and B is the safety window of the rotational speed of the grinding carrier, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

[0031] Specifically, Figure 1 3 is a graph showing the effect of the knife lowering speed and the rotation speed of the grinding stage on the back side damage of the SOI wafer in the embodiment of the present invention. When the knife lowering speed of the rough grinding wheel 32 in the rough grinding process step is controlled within the range of 3 μm / s to 10 μm / s, we tested whether the rotation speeds of different grinding stages 31 would cause damage to the back side of the ground SOI wafer. The results are shown in FIG. Figure 1 shown. Figure 1 The horizontal axis is the cutting speed in μm / s, and the vertical axis is the rotation speed of the grinding stage in rpm. Figure 1The back of the SOI wafer represented by the green data point has no obvious damage, and the back of the SOI wafer represented by the red data point has obvious damage. The test results show that the rough grinding wheel's knife speed and the rotation speed of the grinding carrier in the rough grinding process during mechanical grinding have a significant correlation with whether the back of the SOI wafer is damaged. When the rough grinding wheel's knife speed in the rough grinding process step is controlled within the range of 3μm / s to 10μm / s, the rotation speed Y of the grinding carrier and the rough grinding wheel's knife speed X satisfy the formula Y=BA*X, where X is the rough grinding wheel's knife speed, Y is the rotation speed of the grinding carrier, A is the change in the rotation speed of the grinding carrier corresponding to the change in the unit rough grinding wheel's knife speed, and B is the safety window of the rotation speed of the grinding carrier, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

[0032] The inventors also conducted experimental verification research and set up four groups of experiments. The thickness of the support wafer 10 in each group of experiments is the same, all 773μm. The thickness of the top silicon (the thickness of the device wafer) after the mechanical grinding process is also the same, all 13μm. The lowering speed of the rough grinding wheel 32 and the rotation speed of the grinding carrier 31 in different experimental groups are different. The lowering speed of the rough grinding wheel 32 in the first group is 4μm / s, and the rotation speed of the grinding carrier 31 is 120rpm. The lowering speed of the rough grinding wheel 32 in the second group is 5μm / s, and the rotation speed of the grinding carrier 31 is 200rpm. The lowering speed of the rough grinding wheel 32 in the third group is 7μm / s, and the rotation speed of the grinding carrier 31 is 20rpm. The lowering speed of the rough grinding wheel 32 in the fourth group is 9μm / s, and the rotation speed of the grinding carrier 31 is 100rpm. The formation process of the four groups of experiments is the same. Specifically, two silicon wafers are provided as the device wafer 20 and the support wafer 10, respectively, and the thickness of the support wafer 10 is 773μm; the two silicon wafers or one of the silicon wafers are thermally oxidized to obtain the SOI buried oxide layer; the device wafer 20 and the support wafer 10 are bonded under low pressure, and the low-pressure bonding pressure is 0.01 mbar ~100mbar, for example, 5mabr. After bonding, the SOI wafer with the buried oxide layer undergoes a heat treatment reinforcement process, a chamfering process, an edge corrosion process, and a mechanical grinding process. After the mechanical grinding process, the overall thickness distribution of the SOI wafer is concave, and the thickness of the top silicon is 13μm, that is, the thickness of the device wafer 20 is 13μm.

[0033] Table 1 Damage to the back side of SOI wafer caused by different rough grinding wheel speeds and grinding stage speeds

[0034] Figure 2 This is a back side damage diagram of the SOI wafer in the first group of embodiments of the present invention. Figure 3 This is a back side damage diagram of the SOI wafer in the second group of embodiments of the present invention. Figure 4 This is a back side damage diagram of the SOI wafer in the third group of embodiments of the present invention. Figure 5 is a backside damage diagram of the SOI wafer in the fourth group of embodiments of the present invention. Figure 2~Figure 5 As shown, there is no obvious damage on the back of the SOI wafer in the first and fourth groups, and the damage area is less than the preset threshold, that is, the damage area is less than 5%. The lowering speed of the rough grinding wheel 32 in the first group is 4μm / s, and the rotation speed of the grinding platform 31 is 120rpm. The lowering speed of the rough grinding wheel 32 in the fourth group is 9μm / s, and the rotation speed of the grinding platform 31 is 100rpm. The relationship between the lowering speed of the rough grinding wheel 32 and the rotation speed of the grinding platform 31 in the first and fourth groups meets the preset conditions. However, there is obvious damage on the back of the SOI wafer in the second and third groups, and the damage areas are 50% and 10% respectively, and the damage areas are greater than 5%, that is, the damage area is greater than the preset threshold. The lowering speed of the rough grinding wheel 32 in the second group is 5μm / s, and the rotation speed of the grinding platform 31 is 200rpm. The lowering speed of the rough grinding wheel 32 in the third group is 7μm / s, and the rotation speed of the grinding platform 31 is 20rpm. The relationship between the lowering speed of the rough grinding wheel 32 and the rotation speed of the grinding stage 31 in the second group and the third group does not satisfy the preset condition.

[0035] Based on this, the core idea of ​​the present invention is that the mechanical grinding process includes a rough grinding process, in which the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform meets the preset conditions, so that the thickness of the side of the device wafer away from the supporting wafer is thinned to a preset thickness in the mechanical grinding process and the damage area of ​​the side of the supporting wafer away from the device wafer is less than a preset threshold. The present invention can solve the problem that the damage to the back of the SOI wafer is large in the mechanical grinding process, affecting the performance and reliability of the device, that is, the damage to the side of the supporting wafer away from the device wafer in the SOI wafer of the present invention is significantly improved, thereby improving the performance and reliability of the device.

[0036] Specifically, Figure 6 FIG. 1 is a flow chart of a mechanical grinding method for an SOI wafer according to an embodiment of the present invention. Figure 6 As shown, this embodiment provides a method for mechanically grinding an SOI wafer, comprising: Step S10, providing an SOI wafer, wherein the SOI wafer includes a support wafer and a device wafer, and a buried oxide layer located between the support wafer and the device wafer; Step S20, performing a mechanical grinding process to thin the thickness of the side of the device wafer away from the support wafer to a preset thickness and the damage area of ​​the side of the support wafer away from the device wafer is less than a preset threshold; Wherein, the mechanical grinding process includes a rough grinding process, in which the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding carrier meets a preset condition.

[0037] The preset conditions satisfied by the relationship between the cutting speed of the rough grinding wheel and the rotational speed of the grinding platform include: when the rotational speed of the grinding platform is greater than the preset rotational speed, the cutting speed of the rough grinding wheel is reduced; when the rotational speed of the grinding platform is less than the preset rotational speed, the cutting speed of the rough grinding wheel is increased.

[0038] The preset condition satisfied by the relationship between the lowering speed of the rough grinding wheel and the rotational speed of the grinding carrier is: Y=BA*X; wherein X is the lowering speed of the rough grinding wheel, Y is the rotational speed of the grinding carrier, A is the change in the rotational speed of the grinding carrier corresponding to a change in the lowering speed of the rough grinding wheel per unit, and B is a safety window of the rotational speed of the grinding carrier, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

[0039] Figures 7 and 8 1 is a schematic diagram of the mechanical grinding method of SOI wafer according to an embodiment of the present invention. Figures 7 and 8 The specific embodiments of the present invention are described in detail.

[0040] like Figure 7 As shown, a SOI wafer is provided, wherein the SOI wafer includes a device wafer 20 , a support wafer 10 , and a buried oxide layer located between the support wafer 10 and the device wafer 20 .

[0041] In detail, the step of forming the SOI wafer includes: providing a support wafer 10 and a device wafer 20; the support wafer 10 is used to support the device wafer 20 when the device wafer 20 is thinned. The thickness of the support wafer 10 is, for example, 772 μm to 777 μm. The TTV (Total Thickness Variation) of the support wafer 10 and the device wafer 20 is less than 0.4 μm. The diameter of the support wafer 10 and the device wafer 20 is 200 mm or 300 mm. The device wafer 20 provides an operating platform for subsequent processes. It can be any substrate for carrying semiconductor integrated circuit components known to those skilled in the art. It can be a bare chip or a wafer processed by an epitaxial growth process. In detail, the substrate of the device wafer 20 is, for example, a silicon-on-insulator (SOI) substrate, a bulk silicon substrate, a germanium substrate, a germanium silicon substrate, an indium phosphide (InP) substrate, a gallium arsenide (GaAs) substrate or a germanium-on-insulator substrate. In this embodiment, the device wafer 20 is a silicon wafer. A thermal oxidation process is performed to form a buried oxide layer on the support wafer 10 and / or the device wafer 20; specifically, the thermal oxidation process can be performed on only one of the support wafer 10 or the device wafer 20 to form a buried oxide layer, or the thermal oxidation process can be performed on both of the support wafer 10 and the device wafer 20 to form a buried oxide layer. Those skilled in the art can make a selection based on the thickness of the buried oxide layer. In this embodiment, the thickness of the buried oxide layer is, for example, 0.2 μm to 2 μm. A buried oxide layer is formed on both the support wafer 10 and the device wafer 20, that is, a first buried oxide layer 11 is formed on the support wafer 10, and a second buried oxide layer 21 is formed on the device wafer 20. A bonding process is performed to bond the support wafer 10 and the device wafer 20, and the buried oxide layer is located between the support wafer 10 and the device wafer 20. That is, the first buried oxide layer 11 and the second buried oxide layer 21 are located between the support wafer 10 and the device wafer 20. In other words, the first buried oxide layer 11 and the second buried oxide layer 21 are in contact. After the SOI wafer is formed, the SOI wafer is subjected to a heat treatment reinforcement process, a chamfering process, and an edge corrosion process in sequence.

[0042] like Figure 8 As shown, a mechanical grinding process is performed to reduce the thickness of the side of the device wafer 20 away from the support wafer 10 to a preset thickness and the damage area of ​​the side of the support wafer 10 away from the device wafer 20 is less than a preset threshold. That is, after the mechanical grinding process, there is no obvious damage to the side of the support wafer 10 away from the device wafer 20. No obvious damage is defined as a damage area less than a preset threshold. The preset threshold is 5%, that is, the damage area is less than 5%.

[0043] The mechanical grinding process includes a rough grinding process and a fine grinding process. In the rough grinding process, the mesh number of the rough grinding wheel is, for example, 50 to 800 meshes, and the spindle speed is, for example, 500 rpm to 4000 rpm. In the fine grinding process, the mesh number of the fine grinding wheel is, for example, 1500 to 10000 meshes, and the spindle speed is, for example, 500 rpm to 4000 rpm.

[0044] Since the contact pressure between the SOI wafer and the grinding stage is relatively large during the rough grinding process, the degree of damage to the back side of the SOI wafer (the side of the supporting wafer away from the device wafer) is mainly affected by the rough grinding process. Therefore, in the rough grinding process, the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding stage meets the preset conditions so that there is no obvious damage to the back side of the SOI wafer after grinding.

[0045] Specifically, the preset conditions satisfied by the relationship between the lowering speed of the rough grinding wheel and the rotational speed of the grinding platform include: the lowering speed of the rough grinding wheel and the rotational speed of the grinding platform interact with each other. When the rotational speed of the grinding platform is greater than the preset rotational speed, that is, when the rotational speed of the grinding platform is too fast, it is necessary to reduce the lowering speed of the rough grinding wheel to reduce damage to the back of the SOI wafer; when the rotational speed of the grinding platform is less than the preset rotational speed, that is, when the rotational speed of the grinding platform is too slow, it is necessary to appropriately increase the lowering speed of the rough grinding wheel to avoid damage to the back of the SOI wafer while increasing the removal rate of the front of the SOI wafer. The front of the SOI wafer is the side of the device wafer away from the support wafer.

[0046] In more detail, the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform satisfies the preset condition: Y=BA*X; Wherein, X is the cutting speed of the rough grinding wheel, Y is the rotation speed of the grinding platform, A is the change in the rotation speed of the grinding platform corresponding to the change in the cutting speed of the rough grinding wheel per unit, and B is the safety window of the rotation speed of the grinding platform, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

[0047] Please continue to refer to Figure 8 After the mechanical grinding process is performed, the thickness of the device wafer in the SOI wafer is greater than 12 μm and the TTV is less than 1.5 μm.

[0048] Fig. 9is a schematic diagram of the structure of a mechanical grinding device in an embodiment of the present invention. This embodiment also provides a mechanical grinding device 30 for performing any of the above-mentioned mechanical grinding methods for SOI wafers. The mechanical grinding device 30 includes a rough grinding wheel 32, a fine grinding wheel (not shown in the figure) and a grinding carrier 31. The mesh number of the rough grinding wheel 32 is, for example, 50 to 800 meshes, and the spindle speed is, for example, 500 rpm to 4000 rpm. In the fine grinding process, the mesh number of the fine grinding wheel is 1500 to 10000 meshes, and the spindle speed is, for example, 500 rpm to 4000 rpm. Since the contact pressure between the SOI wafer and the grinding carrier is relatively large in the rough grinding process step, the degree of damage to the back side of the SOI wafer (the side of the supporting wafer away from the device wafer) is mainly affected by the rough grinding step. Therefore, in the rough grinding process, the relationship between the lowering speed of the rough grinding wheel 32 and the speed of the grinding carrier 31 meets the preset conditions so that there is no obvious damage to the back side of the SOI wafer after grinding.

[0049] The preset conditions satisfied by the relationship between the lowering speed of the rough grinding wheel 32 and the rotation speed of the grinding platform 31 include: the lowering speed of the rough grinding wheel 32 and the rotation speed of the grinding platform 31 interact with each other. When the rotation speed of the grinding platform 31 is greater than the preset rotation speed, that is, when the rotation speed of the grinding platform 31 is too fast, it is necessary to reduce the lowering speed of the rough grinding wheel 32 to reduce damage to the back of the SOI wafer; when the rotation speed of the grinding platform 31 is less than the preset rotation speed, that is, when the rotation speed of the grinding platform 31 is too slow, it is necessary to appropriately increase the lowering speed of the rough grinding wheel 32 to avoid damage to the back of the SOI wafer while increasing the removal rate of the front of the SOI wafer. The front of the SOI wafer is the side of the device wafer away from the support wafer.

[0050] More specifically, the relationship between the lowering speed of the rough grinding wheel 32 and the rotation speed of the grinding platform 31 satisfies the preset condition: Y=BA*X; Wherein, X is the cutting speed of the rough grinding wheel, Y is the rotation speed of the grinding platform, A is the change in the rotation speed of the grinding platform corresponding to the change in the cutting speed of the rough grinding wheel per unit, and B is the safety window of the rotation speed of the grinding platform, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

[0051] From the above, it can be seen that in the mechanical grinding method of the SOI wafer provided in the embodiment of the present invention, the mechanical grinding process includes a rough grinding process. In the rough grinding process, the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding carrier meets the preset conditions, so as to reduce the thickness of the side of the device wafer away from the supporting wafer to a preset thickness in the mechanical grinding process and the damage area of ​​the side of the supporting wafer away from the device wafer is less than a preset threshold. The present invention can solve the problem that the damage to the back of the SOI wafer is large in the mechanical grinding process, which affects the performance and reliability of the device, that is, the damage to the side of the supporting wafer away from the device wafer in the SOI wafer of the present invention is significantly improved, thereby improving the performance and reliability of the device.

[0052] In addition, it should be recognized that although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of protection of the technical solution of the present invention.

Claims

1. A method for mechanical grinding of a SOI wafer, characterized in that: include: Providing an SOI wafer, the SOI wafer comprising a support wafer and a device wafer, and a buried oxide layer located between the support wafer and the device wafer; Performing a mechanical grinding process to reduce the thickness of the side of the device wafer away from the support wafer to a preset thickness and a damage area of ​​the side of the support wafer away from the device wafer is smaller than a preset threshold; Wherein, the mechanical grinding process includes a rough grinding process, in which the relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform satisfies a preset condition: when the rotation speed of the grinding platform is greater than a preset rotation speed, the lowering speed of the rough grinding wheel is reduced; When the rotation speed of the grinding platform is less than the preset rotation speed, the lowering speed of the rough grinding wheel is increased.

2. The mechanical grinding method of SOI wafer according to claim 1, characterized in that: The relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform satisfies the preset condition: Y=BA*X; Wherein, X is the cutting speed of the rough grinding wheel, Y is the rotation speed of the grinding platform, A is the change in the rotation speed of the grinding platform corresponding to the change in the cutting speed of the rough grinding wheel per unit, and B is the safety window of the rotation speed of the grinding platform, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

3. The mechanical grinding method of SOI wafer according to claim 1, characterized in that: The mesh number of the rough grinding wheel is 50 to 800 meshes, and the spindle speed is 500 rpm to 4000 rpm.

4. The mechanical grinding method of SOI wafer according to claim 1, characterized in that: The mechanical grinding process also includes a fine grinding process. In the fine grinding process, the mesh number of the fine grinding wheel is 1500 to 10000, and the spindle speed is 500 rpm to 4000 rpm.

5. The mechanical grinding method of SOI wafer according to claim 1, characterized in that: After the mechanical grinding process is performed, the thickness of the device wafer in the SOI wafer is greater than 12 μm, and the total thickness variation of the SOI wafer is less than 1.5 μm.

6. The mechanical grinding method of SOI wafer according to claim 1, characterized in that: The thickness of the supporting wafer in the SOI wafer is 772 μm to 777 μm, and the total thickness variation of the supporting wafer in the SOI wafer is less than 0.4 μm.

7. A mechanical grinding device, characterized in that: A method for mechanically grinding an SOI wafer as described in any one of claims 1 to 6, comprising a rough grinding wheel and a grinding platform, wherein the relationship between the lowering speed of the rough grinding wheel and the rotational speed of the grinding platform satisfies a preset condition, so as to thin the thickness of a side of the device wafer away from the supporting wafer to a preset thickness and the damage area of ​​the side of the supporting wafer away from the device wafer is less than a preset threshold.

8. The mechanical grinding device according to claim 7, characterized in that: The preset conditions satisfied by the relationship between the cutting speed of the rough grinding wheel and the rotational speed of the grinding platform include: when the rotational speed of the grinding platform is greater than the preset rotational speed, the cutting speed of the rough grinding wheel is reduced; when the rotational speed of the grinding platform is less than the preset rotational speed, the cutting speed of the rough grinding wheel is increased.

9. The mechanical grinding device according to claim 7, characterized in that: The relationship between the lowering speed of the rough grinding wheel and the rotation speed of the grinding platform satisfies the preset condition: Y=BA*X; Wherein, X is the cutting speed of the rough grinding wheel, Y is the rotation speed of the grinding platform, A is the change in the rotation speed of the grinding platform corresponding to the change in the cutting speed of the rough grinding wheel per unit, and B is the safety window of the rotation speed of the grinding platform, 5≤A≤10, 100≤B≤200, 3μm / s ≤X≤10μm / s.

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